In countershaft type transmissions, it is well known to utilize mechanical, fluid operated, electrical and electro-mechanical shift controls. These control members generally establish the position of the shift forks which, in turn, control the engagement of synchronizer mechanisms for establishing the drive ratio within the transmission.
In some synchronizer transmissions, it is known to utilize fluid operated clutches in place of the synchronizer mechanisms to establish the drive connection between specific gears and their respective shafts. These control systems utilize a controlled clutch member, which is connected between the prime mover or engine and the transmission. The shift sequence can then be accomplished either manually or automatically as the vehicle is accelerated from a standing start. Generally, the operator will have a shift lever which permits selection of various drive ratios within the transmission, or provides for automatic sequencing of upshifting and downshifting as desired.